This volume contains papers that have been selected after review for oral presentation at ISRM 2015, the Fourth IFToMM International Symposium on Robotics and Mechatronics held in Poitiers, France 23-24 June 2015. These papers  provide a vision of the evolution of the disciplines of robotics and mechatronics, including but not limited to: mechanism design; modeling and simulation; kinematics and dynamics of multibody systems; control methods; navigation and motion planning; sensors and actuators; bio-robotics; micro/nano-robotics; complex robotic systems; walking machines, humanoids-parallel kinematic structures: analysis and synthesis; smart devices; new design; application and prototypes. The book can be used by researchers and engineers in the relevant areas of robotics and mechatronics.